Control device for luminescent lamps

ABSTRACT

A light output control device which includes a controllable bidirectional semiconductor which with its mains current path is connected across the two filaments of a luminescent lamp. The firing moment of the semiconductor can be selectively set, so that the average lamp current in each half cycle of the a.c. voltage across the lamp can be controlled. During the intervals in which the semi-conductor is fired, a compensation current is flowing through the lamp filaments, by which proper ignition of the lamp during each half cycle of power source a.c. voltage is ensured.

United States Patent [191 Laupman CONTROL DEVICE FOR LUMINESCENT LAMPS[75] lnventor: Robert Ronald Laupman, Wijchen,

Netherlands [73] Assignee: Novanex Automation N.V., Wijchen,

Netherlands [22] Filed: Apr. 16, 1971 [21] Appl. No.: 134,590

[30] Foreign Application Priority Data Apr. 17, 1970 Netherlands 7005575[52] US. Cl. 315/105, 315/105 [51] Int. Cl. H05b 39/00 [58] Field ofSearch 315/105 [56] References Cited UNITED STATES PATENTS 3,482,14212/1969 Cluett et al. 315/105 [451 July 17,1973

11/1969 Pagetetal. ..3l5/l05 11/1969 Page! ..3l5/l05 PrimaryExaminer-Nathan Kaufman Attorney-Billet, Brown, Ramik & Holt [5 7ABSTRACT lamp can be controlled. During the intervals in which thesemi-conductor is fired, a compensation current is flowing through thelamp filaments, by which proper ignition of the lamp during each halfcycle of power source ac voltage is ensured.

8 Claims, 8 Drawing Figures Patented July 17, 1973 3,746,919

2 Sheets-Sheet l Fry: .2

' INVENTOR. RBBERT RONALD LAUPMAN ATT DENEYS Patented July l7, 1973 2Sheets-Sheet 2 F33nF 'DOnF ZUZ INVENTOR. NMD LAUPMHN RUBERT R0 CONTROLDEVICE FOR LUMINESCENT LAMPS This invention relates to a device forcontrolling and- /or starting luminescent lamps.

A known circuit diagram for a lighting arrangement including aluminescent lamp capable of being started and operated from a normallow-voltage a.c. power source, is shown in FIG. 1.

In such an arrangement, a luminescent lamp 1, which is provided withcathode filaments 2 and 3, is seriesconnected with a choke-coil 4 forlimiting the operating current and connectable to terminals 7/8 of, forexample, 220 V a.c. voltage. For starting the lamp, a starter 6 isconnected between the remaining terminals of the filaments.

The above arrangement presents an inductive load to the a.c. powersource; it is also possible to use an arrangement which behaves as acapacitive load for the a.c. power source, and compensates the formerarrangement. This can be effected by additionally including a capacitor5 in series with choke-coil 4.

The lamp is started by just switching on the arrangement. The starter 6will then as a rule short-circuit the lamp for some time, in full or inpart, so that the full current which choke-coil 4 is capable of passingflows through the filaments. These are then heated, and when the voltageis subsequently released by starter 6, supply sufficient emission tolight the tube, provided a sufficiently high ignition voltage appearsacross the tube. The construction of coil 4 and series capacitor 5, ifthere is one, is such that when starter 6 breaks the short-circuit path,this ignition voltage does appear across the tube.

When the lamp has been ignited, the waveform of the voltage betweenfilaments 2 and 3, is quite specific for this kind of lamps, and isshown in FIG. 2. The ignition pulse 9 appears in each half cycle,whereafter the lamp is ignited, the voltage decreases to the operatingvoltage value l0, and, irrespective of the operating current, remainssubstantially constant.

Owing to the fact that the'filaments alternately function as cathode andanode, these are maintained in heated condition, they being stronglyheated as anode. This heating is essential, since'the filaments arecoated with an emission enhancing material, which is damaged when theiroperating temperature is 'too low.

This heating is also caused by the fact that the operating current ofthe tube is partially passed through the filaments, which after thestarting process are substantially floating at one end.

For optimal operating conditions, the lamp, its filaments, the coil andthe capacitor, if any are entirely adapted to each other.

Owing to the narrow tolerances permitted by the opcratingconditionsdescribed above, efforts of controlling such luminescent lampshave hitherto only partially succeeded.

It is known to provide filaments 2 and 3 continuously with operatingcurrent through separated windings of a filament current transformer.This, however, results in the filaments being unduly heated when thelamp is operating at its full capacity, so that special constructions ofthe electrodes are required. Moreover, in order to maintain asufficiently high ignition pulse when the lamp is set for a reducedlight output, it is necessary to use auxiliary equipment for generatingthese voltage peaks repetatively across the lamp, since a normal coilwill generally no longer be capable to provide sufficient pulses. For ifthe (sinusoidal) a.c. voltage across the arrangement is decreased, forexample, by means of a control transformer, the current at the end ofthe horizontal portion 10, in FIG. 2, will during the operating periodbe so low that the subsequent voltage peak 9 will hardly, if at all, behigher than the operating voltage 10. The lamp will then begin tooperate in an unstable man ner, and will fail entirely when the supplyvoltage is decreased to a further extent. In the case of a tube for anominal voltage of 220 V, this happens already at a voltage as high asV. When the filaments are allowed to operate at a fixed filamentvoltage, the voltage can be reduced only slightly further by means of acontrol transformer without the ignition pulses becoming intolerablylow. Special auxiliary equipment can then be included to increase thepulses, so that low operating voltages become possible.

It is an object of the present invention to eliminate the drawbacksoutlined above, and to provide a device by means of which luminescentlamps can be controlled in three different ways with the simplestpossible construction, namely: (1) so that the light output of lamps canbe controlled individually; (2) so that the light output of groups ofsuch lamps can be controlled from a central point; and (3) so that thelight output of groups of individually pre-set lamps is subject tocentrally superimposed control.

It is a further object of the invention to provide an electronic controldevice which in modular form can be used as an electronic starter forstandard luminescent lamp arrangements. For this last-mentioned purpose,electronic devices are known in the art, which, however, do not satisfythe requirements which according to the present invention are to beimposed upon a starter for controllable luminescent lamp arrangements.

The invention is based upon the following concept.

If it is desired for a luminescent lamp to be adjusted to reduced lightintensity, this can be effected by causing a lower average current toflow through the lamp, for example, by extinguishing the lamp during aportion of each a.c. voltage half-cycle across the lamp, and if sodesired additionally reducing the operating current during the operatingperiod. In that case, however, the following conditions should besatisfied:

l. the temperature of the electrodes should be maintained approximatelyequal to that existing in the condition when the lamp is operating atits full capacity;

2. the ignition pulse at the beginning of each discharge in the case ofshorter operating intervals should be equal to, but preferably higherthan, that during the condition when the lamp is operating at its fullcapacity.

According to the invention, these conditions are satisfied in asurprisingly simple manner by connecting an electronic current controldevice in place of the original starter, in parallel to the tube, but inseries with the filaments, which device after each desired operatingperiod 10 of the lamp, short-circuits the lamp during each a.c. voltagehalf-cycle across the lamp, and thereby causes a compensation current toflow through the filaments during the period when the lamp isartificially extinguished in this manner 23.

According to the invention this arrangement also leads to the surprisingeffect that when the short-circuit condition of the tube is eliminated,the coil will generate the desired high ignition pulse across the tubewhen the lamp has been adjusted for reduced output. This increase of theignition pulse is so high that, according to the invention, moreover theaverage current through the lamp can be reduced by reducing the mainsvoltage of the overall arrangement, so that as a result of the twomeasures, sufficient compensation current flows through the filamentsduring the artificial extinction of the lamp, whereas the ignition pulseat the beginning of each operating half-cycle remains substantiallyequally high as that during the full-capacity condition.

According to the invention, the control device should preferably becapable of functioning as a starter for the lamp when the combination isswitched on, so that it should also meet the demands to be made on astarter:

Immediately after the arrangement has been switched on, the controlstarter according to the invention should cause a high-current to flowthrough the filaments by largely short-circuiting the lamp, whereafterignition pulses of sufficient amplitude should be generated in the coilto start the lamp (voltage curve of FIG. 4).

When the lamp has been ignited, the control starter will have to shiftthe firing moment to a later instant of time and to such an extent thatthe pre-set operating period of the lamp becomes possible during eacha.c. voltage half-cycle across the lamp, so that the filament current isreduced to the above-described desired compensation current (see thevoltage curve of FIG. 6).

In an embodiment as illustrated in FIG. 3, such a control starteraccording to the invention has been realized in a simple manner.

Such a control starter comprises a capacitor 13, necessary forsuppressing radio interference, connected between terminals 11 and 12.Connected in parallel therewith is a series-circuit constituted by achoke coil 14 and a triac 15. Connected in parallel with the triac is anignition circuit and an RC circuit for appropriately firing the triac.The ignition circuit comprises resistors 20 and 22 and capacitors l9 and21, while diac 18 provides the ignition pulse at the gate of triac 15.

The invention offers two possibilities of controlling the lamp: In thefirst place, the lamp can be controlled individually as follows: Bychanging the values of one of the components 22, 21, 20 or 19, theignition moment can be advanced. The control starter will then beeffective to cut the voltage wave form during each halfcycle andshort-circuit the lamp voltage for a short period. The result is avoltage wave form as shown in FIG. 6. Here again we find ignition peak9, followed by operating voltage 10, whereafter the triac fires and thevoltage in period 23 is reduced practically to zero. The surprisingeffect which then occurs is that, owing to the fact that the coil isactually short-circuited further than during the operating period 10, ahigher ignition pulse will appear across the lamp after the voltage hasbeen reversed. And this is the very thing which is required, since thetemperature of the tube tends to decrease when its operating period isreduced, which renders it more difficult to ignite. Owing to the shorteroperating period, the electrode will no longer be warmed up in I thenormal manner either. In this case, however, the reduced warming-up iscompensated for owing to the fact that during short-circuit period 23the triac again draws filament current through the filaments. Theresulting filament current heating is slightly higher than that whichwould occur during normal operation of the lamp during the comparableperiod. Consequently, the ultimate filament temperature becomes slightlyhigher than normally, which results in smooth and highly uniformoperation of the tube, even in the case of a very short operating period(low light level).

When voltage is applied while the control starter has been set for a lowoutput, the starting-voltage wave form of FIG. 4 will first appearacross the tube until the lamp starts operating, whereafter theoperating voltage wave form of FIG. 6 will gradually be established.Accordingly, the light output of the lamp increases gradually up to thelevel set.

In the second place, the lamp can be controlled, according to theinvention, by varying the a.c. power source voltage, for example, bymeans of a control transformer, if the same control starter is used. Thelatter is then set at such a permanent value that at the nominal powersource voltage of the apparatus, the voltage wave form is just not cutby the control device. When the ignition circuit arrangement is properlydimensioned, the following surprising effect occurs according to theinvention. When the power source voltage of the overall arrangement isreduced, the control starter will begin to cut the voltage wave form. Asthe power source voltage is further reduced, the firing moment will beadvanced more and more. If, in that arrangement, the lamp voltage atfull capacity has the wave form of FIG. 2, the voltage wave form with a"turned low control transformer will be very similar to that as shown inFIG. 6. The ignition peak 9, however, is lower, so that the ignition ofthe lamp in the turned low condition becomes more difficult. Thesurprising effect of the advanced ignition is based on the fact that thelamp voltage increases when the lamp current decreases. This effect canbe explained as follows:

First, the voltage across the tube increases as soon as the currentthrough the tube decreases. As a consequence, the ignition device willjust start igniting.

Owing to the resulting firing of the triac, the powersource voltage ofthe ignition device will be eliminated, and the ignition system will begoing to lead still further.

Second, the further short-circuiting of the coil will cause the ignitionpeak resulting from self-induction to increase. However, this functionsat the same time as a supply voltage for the ignition circuit. This willtherefore contribute towards continuation of the advancement, in spiteof the reduction of the supply voltage of the overall system.

The advancement ultimately arrives at a maximum, with which the minimumworking voltage ofthc system is practically reached as well. Below thatthe tube may be extinguished.

It will be clear that a third possibility is the combination of theabove two main possibilities.

The great advantage of remote control by means of the controltransformer is that it enables a two-wire connection of the arrangement.When the filaments are to be supplied with current separately, thissupply requires the application of an additional line.

Owing to the combined functioning of the control starter, a furtherpossibility offered is to use the starter as an electronic substitutefor the traditional starter, with the additional characteristic that anydesired burning level can be obtained as the final effect, either with afixed or a variable setting. The setting may also be switchable ratherthan controllable.

The dissipation in the control starter is so slight that it may bebuilt-in the standard housing of a traditional starter.

If it is desired to build the arrangement on the basis of standardequipment in the field of luminescent lamps, then it is preferable touse the capacitive embodiment, that is, including series capacitor 5, asthe starting point. This construction has the following advantages.

As a rule, the ignition pulse is higher when the series capacitor isused. This makes the application of the control starter directlypossible with the permissible mains voltage variations of or percent.

Moreover, in the turned low" condition, the arrangement behaves as amore neutral mains load.

Besides there is the risk of failure of the switch element. If thischanges the switch element into a diode, the separation capacitor willbe charged and thereafter no substantial current will flow any longer.The coils are resistant to complete short-circulating of the switchelement.

For standard inductive systems, the voltage can be increased bytransformation, but then it will be necessary to provide safety againstunduly high current.

FIG. 7 shows a more detailed example of a control starter arranged formanual operation. By adjustment of the variable resistor of 100 K, thelight output can be controlled at will. FIG. 8 shows a more detailedexample of a control starter arranged for remote control, for example,by variation of the power source voltage.

I claim:

1. An electrical circuit for use in combination with an ionized arcdischarge illuminating device, said device including power terminals forconnection to a supply of alternating voltage less than a selectedarc-starting level, a pair of electrodes between which the arc may bedrawn during successive half cycles of the supply voltage, and inductivemeans for kicking the supply voltage above a high voltage arc-startinglevel and for limiting the current of the are, said electrical circuitcomprising:

bilateral semiconductor means connected across said electrodes, saidbilateral semiconductor means having a gate electrode for switching thesemiconductor means between a non-conductive state during which ignitionpulses exceeding said high voltage are applied from said inductive meansto said electrodes of the illuminating device and a conductive stateduring which heating current is allowed to flow through said electrodesof the illuminating device; and

timing circuit means connected across said filaments in parallel withsaid bilateral semiconductor means and to said gate electrode thereoffor controlling the state of said bilateral semiconductor means.

2. An electrical circuit as defined in claim 1 wherein said timingcircuit means includes an adjustable ele ment whereby the illuminationintensity of said illuminating device may be varied.

3. An electrical circuit as defined in claim ll including means forvarying said supply voltage whereby the illumination intensity of saidilluminating device may be varied.

4. A starter and illumination intensity control circuit for ionized arcdischarge illuminating devices of the type having a pair of electrodesbetween which the arc is drawn, power terminals for connection to asupply of alternating voltage less than a selected arc-starting level,and inductive means for kicking the supply voltage above a high voltagearc-starting level and for limiting the current of the arc, said controlcircuit comprising:

bilateral semiconductor means connected across said electrodes, saidbilateral semiconductor means having a gate electrode for switching thesemiconductor means between a non-conductive state during which ignitionpulses exceeding said high voltage are applied from said inductive meansto said electrodes of the illuminating device and a conductive stateduring which heating current is allowed to flow through said electrodesof the illuminating device; and

timing circuit means connected across said filaments in parallel withsaid bilateral semiconductor means and to said gate electrode thereoffor controlling the state of said bilateral semiconductor means.

5. A control circuit for ionized arc discharge illuminating devicescomprising, in combination:

a pair of power terminals for connection to a supply of alternatingvoltage lessthan a selected arcstarting level;

ballast means and gate-controlled bilateral semiconductor meansconnected in series across said power terminals; and

timing circuit means connected in parallel with said bilateralsemiconductor means for switching the latter between non-conductive andconductive states.

6. A control circuit as defined in claim 5 wherein said timing circuitmeans includes an adjustable element for varying the time constant ofsuch timing circuit means.

7. A control circuit as defined in claim 6 including means for varyingthe supply voltage.

8. A control circuit as defined in claim 5 including means for varyingthersupply voltage.

1. An electrical circuit for use in combination with an ionized arcdischarge illuminating device, said device including power terminals forconnection to a supply of alternating voltage less than a selectedarc-starting level, a pair of electrodes between which the arc may bedrawn during successive half cycles of the supply voltage, and inductivemeans for kicking the supply voltage above a high voltage arc-startinglevel and for limiting the current of the arc, said electrical circuitcomprising: bilateral semiconductor means connected across saidelectrodes, said bilateral semiconductor means having a gate electrodefor switching the semiconductor means between a non-conductive stateduring which ignition pulses exceeding said high voltage are appliedfrom said inductive means to said electrodes of the illuminating deviceand a conductive state during which heating current is allowed to flowthrough said electrodes of the illuminating device; and timing circuitmeans connected across said filaments in parallel with said bilateralsemiconductor means and to said gate electrode thereof for controllingthe state of said bilateral semiconductor means.
 2. An electricalcircuit as defined in claim 1 wherein said timing circuit means includesan adjustable element whereby the illumination intensity of saidilluminating device may be varied.
 3. An electrical circuit as definedin claim 1 including means for varying said supply voltage whereby theillumination intensity of said illuminating device may be varied.
 4. Astarter and illumination intensity control circuit for ionized arcdischarge illuminating devices of the type having a pair of electrodesbetween which the arc is drawn, power terminals for connection to asupply of alternating voltage less than a selected arc-starting level,and inductive means for kicking the supply voltage above a high voltagearc-starting level and for limiting the current of the arc, said controlcircuit comprising: bilateral semiconductor means connected across saidelectrodes, said bilateral semiconductor means having a gate electrodefor switching the semiconductor means between a non-conductive stateduring which ignition pulses exceeding said high voltage are appliedfrom said inductive means to said electrodes of the illuminating deviceand a conductive state during which heating current is allowed to flowthrough said electrodes of the illuminating device; and timing circuitmeans connected across said filaments in parallel with said bilateralsemiconductor means and to said gate electrode thereof for controllingthe state of said bilateral semiconductor means.
 5. A control circuitfor ionized arc discharge illuminating devices comprising, incombination: a pair of power terminals for connection to a supply ofalternating voltage less than a selected arc-starting level; ballastmeans and gate-controlled bilateral semiconductor means connected inseries across said power terminals; and timing circuit means connectedin parallel with said bilateral semiconductor means for switching thelatter between non-conductive and conductive states.
 6. A controlcircuit as defined in claim 5 wherein said timing circuit means includesan adjustable element for varying the time constant of such timingcircuit means.
 7. A control circuit as defined in claim 6 includingmeans for varying the supply voltage.
 8. A control circuit as Defined inclaim 5 including means for varying the supply voltage.